This Histopathology Core B will be housed at University of Chicago. Core B will be responsible for the histopathological analysis of muscle tissue. The hallmark pathological features of muscular dystrophy include: variation in fiber size, central nucleation, increased extracellular matrix deposition, fatty infiltration, immune cell infiltration, apoptosis, necrosis, calcification and regeneration. Each of these features can be measured either by histopathological examination or by assays that can be performed on an entire muscle. A cardinal feature of the muscular dystrophies is that the pathological findings are not uniformly distributed across a muscle group. To circumvent sampling error that can complicate histopathological analysis, this Core has established quantitative assays that can be used to reflect the process across the entire muscle that is being assayed. This core will provide histopathological examination of the animals generated in the Projects. Quantitative assays across muscle groups will also be performed. Each project will use Core B. The Core's function and output will be overseen by an experienced neuropathologist who has a special interest in muscular dystrophy. The Core will be housed in the Histopathology Core Facility within the Molecular Cardiology/Institute for Cardiovascular Research at the University of Chicago. This facility, established in the early 1990's, has had benefit of stable technical direction and oversight. With the increase in samples to be processed from each of the three Projects in this program, the technical director will supervise the training of new technical staff who will then be responsible for the processing of samples related to the Program.